Glossary of Terms

Capacitance – Measured in farads, it is the opposition to voltage changes in an alternating current circuit, causing voltage to lag behind current; exhibited by two conductors separated by an insulator.

Capacitor – A passive electronic component that stores energy in the form of an electrostatic field. In its simplest form, a capacitor consists of two conducting plates separated by an insulating material called the dielectric. The capacitance is directly proportional to the surface areas of the plates and is inversely proportional to the separation between the plates. Capacitance also depends on the dielectric constant of the material separating the plates.

Choke – An inductor designed to present a high impedance to alternating current.

Clearance – The clearance is defined as shortest distance through the air between two conductive elements.

Common Collector Connection – Same as grounded collector connection. Also called the emitter-follower. A mode of operation for a transistor in which the collector is common to both the input and the output circuits and is usually connected to one of the power rails.

Common Emitter Connection – Same as grounded emitter connection. A mode of operation for a transistor in which the emitter is common to the input and output circuits. The base is the input terminal and the collector is the output terminal.

Conductivity – How easily something allows electric current to pass through it. If a substance is a good conductor (highly conductive), for example copper or brass, it will allow electrons to pass freely through it, offering only minor resistance.

Corona – A luminous discharge due to ionization of the air surrounding a conductor caused by a voltage gradient exceeding a certain critical value.

Corona Extinction Voltage (CEV) – The highest voltage at which a continuous corona of specified pulse amplitude no longer occurs, as the applied voltage is gradually decreased from above the corona inception value.

Corona Inception Voltage (CIV) – The lowest voltage at which a continuous corona of specified pulse amplitude occurs as the applied voltage is gradually increased.

Creepage Distance – The shortest distance separating two conductors as measured along a surface touching both conductors.

Dielectric – Non-conducting material used to isolate and/or insulate energized electrical components.

Dielectric Constant (K) – The property of the dielectric material that determines how much electric energy can be stored in a capacitor of a particular size by a value of applied voltage.

Dielectric Strength – The maximum voltage an insulating material can withstand without breaking down.

EMI, RFI – Acronyms for various types of electrical interference; electromagnetic interference and radio-frequency interference.

Hi-Pot Test (High Potential Test) – A test performed by applying a high voltage for a specified time to two isolated points in a device to determine the adequacy of insulating material.

Impedance – (Z) Measured in ohms it is the total opposition to the flow of current offered by a circuit. Impedance consists of the vector sum of resistance and reactance.

Insulation Resistance – The resistance offered, usually measured in mega ohms, by an insulating material to the flow of current resulting from an impressed DC voltage.

Insulators – Materials that prevent the flow of electricity. Nonconductive materials used to separate electric circuits.

Inverter – An electric or electronic device for producing alternating current from direct current.

Partial Discharge – A type of localized discharge resulting from transient gaseous ionization in an insulation system when the voltage stress exceeds a critical value.

Resistance – R and measured in ohms. Opposition to current flow and dissipation of energy in the form of heat.

Self-inductance – The property of a conductor that produces an induced voltage in itself with changing current. The term inductance alone means self-inductance. When a varying current in one conductor induces a voltage in a neighboring conductor, the effect is called mutual inductance.

Shield – Partition or enclosure around components in a circuit to minimize the effects of stray magnetic and radio-frequency fields.

Shunt – A low-value precision resistor used to monitor current.

Snubber – A resistor-capacitor (RC) network used to reduce the rate of rise of voltage in switching applications.

Voltage Drop – Conductors carrying current always have inherent resistance or impedance to the current flow. Voltage drop is the amount of voltage loss that occurs through all or part of the circuit due to impedance.

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